The long-term goal of this study is to develop systems for foreign gene expression in rat airway epithelia in vivo, which can be applied to the development of gene therapy for cystic fibrosis. Specifically, the E.coli lacZ gene will be used as a reporter gene to design retroviral vectors that obtain the stable, long-term expression of beta-galactosidase in cultured airway epithelia from both rodents and humans. An in vivo epithelial culture system in denuded tracheas will be used to evaluate cell differentiation and longer-term gene expression. Systems will be develop to achieve foreign gene expression in intact airways of neonatal and adult rats. Cells transduced in vitro will be instilled into airways to determine if a grafting approach is feasible. In addition, direct vector infection of the airways will be attempted by instillation of vector stocks and by inhalation of aerosolized virus. Through these studies, we intend to determine the optimal parameters to achieve stable, high-level transgene expression in airway epithelia and to maximize the number of transduced cells in vivo.